I'm no expert, so this could be inaccurate, but I think you'd have one of two scenarios:

1) After you bought your bitcoins, you transfer them out to your own wallet. These are completely safe even if the exchange goes wallop.

2) You store them on the exchange, in which case you are screwed.

So assuming that you are talking about immediately withdrawing to your own wallet after you've purchased, then yes, you are safe

Rit.